Astrocyte Heterogeneity or Homogeneity?

V. Parpura and P.G. Haydon (eds.), Astrocytes in (Patho)Physiology of the Nervous System, 1 DOI: 10.1007/978-0-387-79492-1_1, © Springer Science + Business Media, LLC 2009 The history of the morphology and electrophysiology of the neuroglia , which was the historical term used for what are now termed astroglia or astrocytes, is briefly reviewed. The interpretation of these data around 1970 was that astroglia in situ represented a homogeneous electrophysiological phenotype with a major function, based on this, in maintaining a constant extracellular concentration of potassium ions ([K + ] o ). It was soon found that astroglia in situ played a major role in the uptake and inactivation of the synaptically released amino acid transmitters glutamate and γ-aminobutyric acid. Subsequent studies in isolated systems, such as primary astrocyte cultures, greatly expanded this view to a more protean cell, with much wider properties in terms of transmitter uptake systems and release, a variety of voltage-dependent ion channels and varying membrane potentials and electrophysiological behaviour, and receptors for a large number of neurotransmitters.